1. Field of the Invention
This invention relates to booster pump systems, and more particularly to a booster pump with constant pressure controller which automatically detects the pressure of the water supply pipe, and changes the speed of the motor subject to the pressure detected.
2. Description of the Prior Art
A variety of booster pump systems have been developed, and intensively used in high-rise buildings for pumping water from a water supply pipe system under the ground to a water reservoir on the roof. These booster pump systems are commonly controlled by a pressure switch. When the pressure in the supply line drops below the preset level, the motor starts to drive the pump. On the contrary, when the pressure surpasses the preset level, the motor stops. Because the pressure switch is frequently turned on and off, the switching contact tends to be fused.
Another drawback of these conventional booster pump systems is that the pressure of water changes sharply during the operation of motor, thereby causing the hot water can't be supplied under a steady condition when in a shower. Still another drawback of these conventional booster pump systems is their high consumption of electric power, because the consumption of energy is directly proportional to the starting frequency of the motor. When the pressure of water drops below the preset level, the motor will immediately turn on at full speed. Therefore, much power supply is consumed during the operation of the system.
There is known an inverter controlled booster pump which, as shown in FIG. 1, is comprised of a pressure meter, a pressure transmitter, a PID (Proportion Integral Differential), an inverter, and a pump. The PID controls the inverter to change output frequency to the pump subject to the pressure of the water supply pipe detected by the pressure transmitter, causing the speed of the pump to be regulated. However, this structure of inverter controlled booster pump system is expensive to manufacture. Furthermore, the operation of this inverter controlled booster pump system tends to be interfered with external magnetic waves because the pressure meter, the pressure transmitter, and the PID are separately installed.